The choice depends on several design and operational factors, including: 

• Cooling system configuration
• Ceiling height and return air pathways
• Raised floor vs slab construction
• Retrofit vs new-build scenario
• Working environment requirements for personnel 

Hot-aisle containment often supports higher efficiency and provides a more comfortable ambient room temperature for personnel. Cold-aisle containment is often easier to retrofit and requires fewer structural modifications. 

In practice, relatively small design constraints often determine the final decision.